The 340 is out....again.....

RPM heads will not affect the lower end. The lower end affects the lower end. What were the clearances on this last rebuild? Was the camshaft changed during the 2nd rebuild? What had to be done to the cam bearings during asembly to allow the cam to turn? What did the mains and rods look like upon disassembly? Was the timing set re-used? Was the oil pump re-used? Was the block magnafluxed this second time around?
Two lower ends have been damaged the same way. The shop did not actually find and fix the original cause.